i done fucked up

so a few weeks ago at the office, they are assigning schedules. I knew i was gonna get a shitty one, as the new guy. It came down to either sunday-thursday 2nd shift, or tuesday- saturday, 2nd shift. I needed that sunday off. That one sunday. Just the one. So what did i do? I erased all of my friday and saturday nights for the forseable future. Didnt even realize it until last weekend. This should teach me to not make important decisions when im sober, but it wont.